Instructions for use

Title Chromosome Structure and Behaviour in Some Plants I. Chromosomes of Diphylleia Grayi FR. SCHM

Author(s) SOEDA, Toru

Citation Journal of the Faculty of Science, Hokkaido Imperial University. Ser. 5, Botany, 5(3), 233-248

Issue Date 1942

Doc URL http://hdl.handle.net/2115/26270

Type bulletin (article)

File Information 5(3)_P233-248.pdf

Hokkaido University Collection of Scholarly and Academic Papers : HUSCAP

Chromosome Structure and Behaviour in Some Plants I., Chromosomes of Diphylleia

Grayi FR. SCUM.

By

TORU SOEDA

(With 8 text-figures)

The spiral structure ,of meiQt~c chrQmQsQmes has been described by many wQrkers in variQus plants. There are, hQwever, yet many unsQlved impQrtant prQblems and cQnsiderable difference ,of QpiniQns amQng in­vestigatQrs, regarding the ,origin and nature ,of spiral strul.lture ,of chrQmQ­SQmes. TQ make clear these questiQns and tQ cQnfirm the universality ,of the facts ,observed by previQus wQrkers, further investigation with many suitable materials and excellent methQd may be demanded.

The present material, Diphylleia Grayi FR. SeRM., belQnging tQ Beri­beridacae, prQves tQ be favQrable fQr karyQIQgical studies due tQ the fQllQw­ing reaSQns: 1) Its 1,0* number ,of large chrQmQsQmes, i.e. 6 in haplQid. 2) The manifestatiQn ,of spiral structure ,of meiQtic chrQmQsQmes being relatively easy. 3) The mQrphQIQgical differentiatiQn ,of each chrQmQsQme being clear except fQr ,one pair.

In the present paper the details ,of mQrphQIQgical features ,of chrQmQ­SQmes in this material were made clear and SQme QbservatiQns ,on the structure ,of meiQtic chrQmosQmes were repQrted preliminarily.

CQncerning karyQIQgical studies ,on this plant, there is ,only ,one repQrt ,of MATSUURA and SUTO (1935), in, which they have made clear the chrQmQ­SQme number ,of it tQ be n=6, and they have furthermQre suggested that the cQmplement ,of this plant cQnsists ,of tWQ pairs each ,of median, sub-

• median and subterminal chrQmQsQmes. In ,other species, Diphylleia cymosa, LAN9LET (1928) has cQl.mted twelve chrQmQsQmes in sQmatic cells.

BefQre gQing further, the writer wishes tQ express his heartiest thanks tQ PrQf. H. MATSUURA fQr his valuable suggestiQns and criticism in the CQUrSe ,of the present wQrk. His thanks are alsQ due tQ the Scientific Research Fund ,of the Department ,of EducatiQn, by a grant frQm which this wQrk was supPQrted.

234 T. SOEDA

Material and Method The material used in the present study was collected on l\1t. Soranuma

near Sapporo and it was transplanted in the experimentai gardens of our Laboratories for the investigation of meiosis, because the meiosis of this plant usually begins at the end of March or in April under snow, and this renders getting material at such time in natural habitat very difficult.

For the determination of somatic complement the root-tip cells were employed. They were fixed with La Oour 2BE and then sectioned in paraffin at a thickness of 26 microns. The slides were stained with gentian­violet after the NEWTON'S schedule.

In some cases chloralization was tried to make clear the morphological characteristics of chromosomes by the following trJatment: after rootlets were immersed together with rhizome in 1 % chloralhydrate for one hour, rinsed in running water for 30 minutes, and allowed to remain for three or four hours in wetted saw-dust (18°-'-20°0), ~he root-tips were cut and fixed with the described solution. This treatment proved to be very effec­tive for the aim mentioned above.

To observe the morphological influence of low temperature on the chromosomes, several rhizomes were buried in wetted saw-dust and kept in the chamber of 5°0 for 7 days.

For the study of structural details of meiotic chromosomes in PMOs, , MATSUURA'S water pretreatment (MATSUURA, 1938b) wa~ tried. The proce­

dure is {ls follows. The pollen mother cells are smeared on a slide and then one or two drops of tap water are quickly added on them. 'l'he water is left on the material for two minutes (the time needed for treat­ment varies according to material) and then the excess of water is removed. as far as possible, with blotting paper. The fixing solution, LA OOUR 2BE, is dropped quickly on the material pretreated' with water to make, permanent the preparations which are then very carefully washed in running water. The slides are stained with gentian violet after the NEWTON'S schedule. This treatment gives satisfactory re'sult in this material.

Observations i. Somatic chromosomes. The somatic complement of this plant

contains twelve large chromosomes consisting of two pairs of median, sub­median and subterminal ones on the position of kinetochor~ (Fig. 1, 2). This agrees completely with the snggestion of MATSUURA and SUTO (1935)

. '

Chromosome structure and behaviour in some plants I

c

Fig. 1. Somatic metaphase showing 12 chromosomes. a, from the material . treated with 1 % <1hloralhydrate.' b, non-treatment. c, from the material cooled in 5°C for 7 days. x 2000.

235

as mentioned above. The six pairs, furthermore, are 'able to be classified into five types of A, B, C, D and E according to the relative length1 ) of their arms and the other morphological characters (Fig. 2). Type A, Containig two pairs of chromosomes with median kinetochore

and being the longest of the complement. Al is very difficult to be distinguished from A2 morphologically.

Type B, The whole length is shorter than type A, though the long arm is approximately equal to that of A. The kinetic constriction is situated at about a third of whole length.

'Type C, Having submedian kinetochore; the ratio of the length of the long arm to that of the short arm is about 7.0 to 4.5. The whole length is about equal to that of B. The long arm is approximately equal to that of E, and it is the shortest long arm in the complement. This type is easily distinguished from B with a clear secondary con­striction situated at about central position of the short arm.

'Type D, The long arm is the longest, but the short arm is the shortest in the complement.

1) The actual length of each chromosome was not measured in the present study, because the chromosomes of this plant are exceedingly large, consequently it is too difficult to measure their true length accurately. The relative length, however, were determined on the preparations treated with chloralhydrate, as the chromosomes are shortend and straightened by the treatment (Compare Fig. 2a with Fig.2b).

236 " t T. SOEDA

( At Az B c D E

Fig. 2. Chromosomes classified from the Fig. 1, upper group from a, lower group from b. s shows the 'region of the secondary constriction. x 2000.

Type E, The shortest chromosome III the' complement: The prominent mark of this chromosome is the trabant or secondary constriction OIl

the short arm. ii. Nucleolus. In the present material the number of nucleoli in

telophase nuclei of somatic cells was two to four (Fig. 3a, b), but a nucleus

o

"

o

. ,

..

Chromosome sh'ucture and behaviour in some plants I 237

having more nucleoli than four was not seen. Considering the number of secondary constric­tion in the present material, the fact mentioned ~bove, as far as the number of. nucleoli i!<'COll­

cerned, agrees with HEITZ'S

theory (1931 a, b) that the nucleoli originated in the satel­lite stalk of SAT-chromosome or secondary ~onstriction ~n telo­phase, and that the number, position' and size of the nucleoli correspond to those of these

, I

a'a ~ , II At Az BCD E

-Jl a ~ ( { ( Fig. 3. Chromosomes classified from the Fig. lc. s shows the region of the secondary. constrie· tion. x ~OOO .

regions of SAT-chromosome or secon'dary constriction present in the nuclei. The writer, however, could not completely confirm the HEITZ'S theory, as the direct observatjon on the relationship between nucleoli and chromosomes has not been done in the present study. There are, indeed, some reports

.~ ~ .@

.~ @

(f.i) b

Fig. 4. a shows nuclei having various numbers of nucleoli. Notice that, the more the number of' the nucleoli decreases, the larger·the volume of nucleoli becomes. h represents telophase nuclei showing four nucleoli. x 1500.

/

•

/

- J

,.

., J

238 T. SOEDA

asserting that the secondary constrictions have no connection with the nucleolus (HEITZ, 1933; KAUFMANN, 1934, 1937; FERANDES, 1936; MATSU­URA, 1938; OKUNO, 1937; RESENDE, 1937; SATO, 1936a, b, 1937). The decrease of the number of nucleoli in the late telophase or resting stage may depend upon the result of their fusiol1 (Fig. 4a). •

In meiotic prophase the nucleolus usually was only one, but sometimes three or four nucleoli instead of two were observed in the nuclei of the first telophase (Fig. 5a). This fact 1!I!ay depend upon the reason that the paired chromatids of a chromosome' are already separated from each other

a b

Fig. 5. a is a PMC in fhst. telophase, showing the two. nuclei having three and four nucleoli. b is a PMC of t~trad stage. x 1200.

in. the first anap~ase, attach­ing only at the .position of kinetochore, so. the nucleoli originate independently on each separated chromatid of the nucleolar chromosome in the telophase. 'But it IS

naturally supposed that the nucleoli formed on each separated chromatid of nu­cleolar chromosome may be apt to fuse easily, for the sake of the interval of· the separat­ed chromatids being very limited. In tetrads stage the

numbers of ,nucleoli-were counted usually one or two per nucleus (Fig. 5b). iii. The influence of treatments on the chromosome. a. The influence of chloralhydrate (refer. Fig. 1a and 2). Some

remar~able influences of chloralhyarate with the method described are as follows; (1) Contraction of the chromosomes and less twisting are evident. (2) The kinetic constriction becomes .very pronounced and elonga~ed, but secondary constriction or akinetic constriction remains intact as ~bserv'ed by RAGA (1940).' (3) Chromosonies are spread out in ~yto­plasma. The degree of these influences is different in diff~rent cells.

b. The influ~nce of low temperature (refer. Fig. lc' and 3). (1) The reaction of "I" in chloralization is also verifiable in this treatment, but the degree of contraction of chromosomes in each cell, is mOl~e variable

. than in the case of chloraIization, i.e., there are cases which show more contraction than that of chloralizat'ion, and at the same time, cases which are not con~iderably different from the control. The degree of influence,

\ ~

o

Chromosome structme, and beh/lviom in some plants I 239

however, is always constllnt in one cell. The causes that even the in­fluence under the same treatment shows various degree in each cell may be partly attributed to. differences in each cell's stage when the stimulus was initiated. (2) The elongation of kinetie- constriction is never seen in this treatment: this shows remarkal)le contrast to the case of chloralization. (3) The secondary constriction does not show -any conspicuous difference

, from that of the control in this treatment too, although in some cases it contracts very slightly. (4) Chromosomes become rather crowded, instead of spreading as seen in chloralization. (5) The dividing figNres are much :rarer than In the control.

Ttl give a critical explanation for. the facts mentioned above/ is beyond the present study, but, at least, the elongation of kinetie constriction seems to occur independeent of the contraction of chromosomes. In contrast to the kinetic constriction, it is further interesting to notice that the secondary con~triction shows no remarkable difference between the cases treated with chloralhydrate and low temperature and the case of non treatment, although in some cases under low temperatur~ there is a slightly greated construction than jn those of the control.

iv. Meiotic chromosomes. Chromosome behavior during the prophase was not studied. Metaphase pairing is usually regular, showing 6 bivalents paired with many chiasmata and sometimes with kinetochores and chias~ mata (Fig. 6, 8). The· failure of pairing was once obesvred in each of median and submedian chromosomes (Probably A and B; Fig. 7a, b). MATSUURA and. SUTO (1935) have frequently ob­served four univalents in one nucleus, but the occurence of more univalents than two was not met with ih the present study.

The chiasmata were mostly interstitial, the terminal chiasc

. mata being ,rare (Table 1). The maxi~um frequency of chias­mata in one chromosome was 5 as observed in A type chromo­some.

. ,

Fig. 6. A first metaphase of PMC, showing 6 bivalents. The spiral structure was demon­strated with MA~suuRA's water pretreatment. The directiqn of coiling is partly indistinct, especially in the chiasma loops. k shows kineto­chore. x 2450 .

, I I

240 T. SOEDA.

a Fig. 7. a and b show the unpairing of median and submedian

chromosomes respectively. x 2450.

Table 1. Chiasma frequency in 20 PMCs. The association of the kinetochores is not included. M, SM and ST show median, submedian and

subtel'minal chromosom,es respectively.

Interstitial Terminal Total . Type of chiasmata chiasmata

chromo-frequency frequency frequency some actual actual actual

number per number per number per bivalent bivalent bivalent

M 1i8 2.95 6 0.15 124 3.10

S. M 73 1.83 8 0.20 81 2.03

S. T 58 1.45 4 0.10 62 l.55

Total 249 2.07 18 0.15 ·267 2.23

I

The identification of each chromosome is difficult in the first metaphase of, PMC unless' the spiral structure of chrom0nema is demonstrated. The kinetochore becomes recognizable as a somewhat spherical body well stained,' when the spiral structure was manifested. •

The representation of the kinetochore and the comparison of turn numbers of the spiral of each chr6mosome help the' identification of each chromosome.

o

Q

-. j

o

"'

C,hromosome structure anq behaviour in some plants I 241

. The spiraP) of chromonemata of this material are more slender,than those of Trillium and ,Tradescantia. It is somewhat difficult to count strictly the turn' numbers of each chromosome on account of the e:xistence of pumer.ous chiasmata: The rough nunibers of turns in each arm of all chromosomes are shown in Table 2. 'This data correspond well with the relative len'gth of somatic chromosomes.

, Table 2. The number of turns in each arm of all chromosomes.

Type of Long arm Short arm Distal part from Total chromosome seconQal'Y cQnstriction

.ft.-A. 9± 9± 18± . B 9± 4.5-5. . 14± . , C 7.5± 3- 3- 13±

" D 10± 0 10±

E 7± 0 , 1- 8± ,

Remarks: The numbers of turns of each chromosome is more or less different in cells.

The fact that the, direction of major spirals changes frequently along the whole length of the chromonemata within the meiotic-chromosomes has been observed by many workers' iri various materials. Such change in direction of spirals is usually found to occur at the kinetochore as seen in Fig. 8a, b (HUSKINS and SMITH, 1935;, HUSKINS and WiLSON, 1938; IWATA, 1935, 1941;. MATSUURA, 1935b,i1937a,b; NEBEL, 1932; SAX, 1930, 1935; SAx and HUMPHREY, 1934;:SHIN~E, 1934; TAYLOR, 1931; TOYOHUKU (the present writer who, meanwhile, has change<i'Itis name), 1939), and at the point of interstitial chiasmata (Fig. 8a, b, d and 1; HUSKINS and SMITH, 1935; HUSKINS and WILsON, 1938; IWATA, 1941; SAX, i9,36), how­ever, sta~istical investigation was not done in the present study. Besides those cases,-' reversals in direction of spirals occur also within the whole arm

\

or a part' of arm. Within -the loop of chiasmata", the spiralsfrequntly take incomple;te form, especially in cases where the loops of chiasmata are small,.as reported by MATSUURA (1941), but the perfect corrugated form (Fig. 8c) observed in Trillium (MATSUURA, 1941) seems to be rare in the present material.

1) As far as no other r'lmark is given, "spiral" means th~ major spiral of the chromonema of the nrst metaphase in PMC ,in the present study. .

\

,

242

R

k

T. SOFJ)A

R ~ . ~R .

. L j~ A .. ~A ~~Ll .L ,

L k k .cr' ,R k

k R ~.L ~

c

b . C

j

B'

i

k~ .,~~~:r{ L k L. D., "

1 _Fig. 8. 'Chromosomes of the first metaphase drawn from various PMCs. The symbols of R, L, k and A-E show dextrors-e, sinistr6"rse spiral, kinetochores and types of chromosomes respectively. x 3550.

o

c·

o

; r~

Chromosome structure and behaviour in some plants I 243

-The configuration of spiral structure in the loop' ot interstitial chias­mata and of free arms is shown in Table 3 and 4 respectively.

Table 3. Structure of loops of interstitial chiasmata.

No. of turns Configuration No. of loop- Freq. of reversal and type of arms arms observed . (Per 100 turns) I

---4 (Bs) ~: (Fig. 8i) 0

4 (A) L, .•. R, .•. L,

R. 2

4 (A) R. 10 0 4 (10%) R.

4 (A) R L~ (Fig. 8d) , 1 , .. .

4 (Dl) L •. R. 1 L.

4.5 (A) R •.•. L. (Fig. 8e) R •.•. L.

2

5 (A) R •.•. L •.•

1 L.

5 (E1) R,.L. Ra.L.

10 2 ' 6 (12%)

5 (B1) ~: (Fig. 8h) 0 ,

5 (Dl) ~ (Fig. 81) 1 R •.•. L •.•

6 (A) Lo·.R •. L, .•

} - ..

R •.• La·• 3

} Lt .•. R •.• I

6 (A) 6 1 4 (11.1%) R •.

6 (A) R. . ) 0 L. (FIg. 8d , •

7.5 (A) L •. Ra.• (F'· 8f)

~ 3

} 4 (12~5%) R •.•. La.R. Ig. 4

7.5 (Dl) ~ J 1 R •. La .• "

Total Actual Expected Dev_ ratio ratio •

Total of dextrorse spirals· 75.5 0.97 1.00 -0.03 155.0

,; sinistrorse spirals 79.5 1.03 1.00 +0.03 Remarks: In the above table, loops formed between' two chiasmata, and,

between a kinetochore and a chiasma were dealt with. Loops in­cluding the kinetochore in the loops were excluded.

. .

24:4

No. of turns and type of 'arms

3 (A} ,

3 (Dl)

, 4 (E1)

3.5 (A)

3.5 (Bl)

'.4 (Bl)

3.5' (A) ,

4 (A)

4 (A)

4 CA.)

I 4 (A)

':lo5 (Bl) ,

. 5 (A)

, 4.5 (Bs)

5 (A) . 4.5 (A)

4.5 (A) . . ' 5 (Bl)

a (El) . 4.5 (A)

4.5 (A)

'T. SOEDA N

Table 4. Structure of free-arms.

Configura tion No. of loop-

arms observed

Ro ~

J L~ 4 Lo Ro

R. L.

Lo .• Ro .•

Ro .• (F' . R 1g• 8J ) 0'.

L. -R. ~ R •. LI .•

L. 20

L. RI.Lo . Lo.N. '

L" R. R.

J R.

Ro .• , Lo .•

~

1 :ft1 .•• L •.• R •. L •.•

(Whole arm) Lo .•

R. L.

L : R •.• R •.• R •.• R •.• L. R. L. R.

L •.• R •.•

L •. R .... .. L •.• ,

Freq. of reversal (Per 100 turns)

0

(I I

0

0

0

1 3 (3.8%)

0

2

0

0

J 0

1 1 1

0

0

0 3 (3.3%)

0

II

Q

1

•

Chromosome structure and behaviour in some plants I 245

6 (Dl) ~ 1 ~ L •.•. R1 •• t

6 (Dl) L. 0

L.

5.5 (C.) L •.•. R. (Fig. Sk) R. .•. L. _ 10 .2 3 (5%)

6 (A) L.

0 L.

5.5 (A) R'.5 0 )

L •.•

R •.• / 6.5 (01)

R •.• 0

6.5 (A) R •.• 0

L •.•

R •. L. 8 3 (5.4%)

7 (Dl) I.. 2 L •. R1

7 (Bl) ~ 1 R •. L.

, L •.•. R •. ~

8.5 (Dl) R •.•. L •.•

2

8.5 (A) L···(Whole arm) (Fig.8b) .R... . 0

9 (A) L:" . ~ (Whole arm) R. 0

S.5 (D1) R •.•

f

14 1 Ii (6.35%) L.;R •.•

L •. R, ( ) (Fik, Si) 2 9 (B1) R •. La

Whole arm

8.5 (A) ~ (Whole arm), (Fig. Sa)

J 1

R •.• L. .

L a ••• R1 ••• L •.• -

J 8.5 (A) (Whole arm) 2 L •.•

Total Actual Expected Dev. ratio ratio Total of dextrorse spirals 197 0.97 . 1.00 -0 .. 03

sinistror~e spirals 406

1:03 "

209 1.00 +0.03

In those tables the symbols of Rand L mean dextrorse and sinistrorse spirals respectiv:ely, ana the 'figures of right side of the symbols show the number of turns. The numerator and denominator of the conilguration in the Tables represent the configuration of two arms; it was provided that· recording always starts' from the proximal region and ends at the distal

246 T. SOEDA

region. In calculati9n of the frequency of reversals fractional numbers such as 4.5 or 5.5 are calculated' as 5 or 6 respectively.

As seen in the above Tables, the frequency of reversals in the loops of interstitial chiasmata is high as compared with the frequency of reversals in free arms. MATSUURA (1941) has observed the same fact in Trillium and has interpreted it as follows: ""Free" strands are able to rotate in spiralisation and consequently the parallel arrangement of the paired chromatids can be converted into th~ twisted orientation in spirals, that is, the relational spiral, while in "fixed" strands their freedom of rotation is prevented and therefore· the paired chromatids take more complicated configurations, as the present paper has shown. - In the latter, the paired strands will assume either a relational spiral in the .form of a b~lanced spiral or a parallel one in the form of an unbalanced spiral." The data of the present study, seem to support MATSUURA'S statement, although the clear "balanced type" as, observed by him was not met with. The observa­tion in the loops including terminal chiasmata was not done in the present study. The frequency of reversals in free arms shows. a clear association with the number of turns, as'seen in Table 4 (MATSUURA~ 1935b, 1937a, b; HUSKINS and WILSON, 1938). In free arms theratio'of the total number of dextrorse spirals to that of sinistrorse spirals is approximately as 1 to 1 (Table 4), suggesting that the direction of spirals is subjected to the law of chance, I:tS observed by MATSUURA (1935b, 1937b) in Trillium.

The present study is not -yet enough, to give a conclusive view on the structure of the meiotic chromosome of' this plant, but" at least" the data of the present study seem to be well in accordance with those observed by MATSUURA (1935, 1937a, b, 1941) in Trillium kamtschaticum.

The studies on the structure and behavior of the chromosomes in the succeeding stages are left for nea,r future, when sufficient data may be' at the writer's disposal.

, Summary 1. The chromosome number of Diphylleia Grayi was confirmed to be

6 in PMO and 12 in sdmatic cells. The chromosomes were classified into five types of A, B, 0, D and E, according to their relative length and other morphological characters. \ ,

2. The tr,eatments of l<iw temperature and chloralizatiolJ. were tried on the somatic chromosomes. The, manner of reaction' of the kinetic con­striction is different under each treatment. ,

3. The major spirals of the chromonemata in the first meiotic meta-

o

•

•

•

, '

o

Chromosome structure and behaviour in some plants I 247

phase were studied. Some statistical analyses were made on the direction of spirals in free arms and of the loopsrof interstitial chiasmata.

4. The reversals of the direction of spiral in free arms· in the first meio~ic metaphase were confirmed to be propotional to the number of turns and it seems not to be associated with chiasmata. . \

5. The frequent reversals of the direction of spiral were observed III

the loops of interstitial chiasmata. These frequent rev~sals seem to Mn­firm MATSUURA'S statement.

Literature cited FERNANDES, A., 1936. Les satellites chez les Narcissus II. Les satellites pendant la

mit9se. Bol. Soc. Broteriana 11 (II serie): 249-277. HAGA, T., 1937. Karytypic polymorphism, in Paris hexaphyUa Cham., with special re­

ference to its origin and to the meiotic chromosome behavior. Cytologia Fujii Jubi. Vql.: 681-700. }

HEITZ, E., 1931a. Die Ursache der gesetzmassigen Zahl, Lage, Form und Grosse pflanz­licher Nukleolen. Planta, 12:.284-291. 1931b. Nukleolen und Chromosomen in the Gattung Vicia. Planta, 15: 495-505. 1933. Die somatische Heteropyknose .bei Drosophila melanogaster und ihl·e· genetische Bedeutung. Zts. Zelf. u. mikr. Anat., 20: 237-287.

HUSKINS, C. L. and S. G. SMITH, 1935. Meiotic chromosome etructure in Trillium ·erectum L. Ann. Bot., 49:.119-150.

HUSKINS, C. L. and G. B. WILSON, 1938. Probable-' cause of' the changes in direction of the major spiral in Trillium erectum L. Ann. Bot. N. S. 2,: 281-291.

IWATA, J., 1935. Chromosome structure in Lilium. Mem. ColI. Sci. Kyoto Imp. Univ. B, 10:2]5~288.

-- 1941. Studies on the chromosome structurEj III. The spiral structure of TriUium chromosomes in fixed material. Jap. Jour. Bot., 11: 439-450.

KAUFMANN, B. P., 1934. Somatic mitosie of prosophila melanogaster. Jour .. Morph., 56: 125-155.

-- 1937. Morphology of the chromosomes of Drosophila ananaSS6. Cytologia Fujii Jubi., Vol.: 1043-1055.

LANGLET, 0., 1928. Einige Beobachtung liber die Zytologie der Beriberidazeen. Svensk Bot. Tids.,22 : 169:'189.

MATSUURA, H., 1935a. Chrom~some studies on Trillium 7camtschticum Pall. 1. The number of coils in the chromonema of the normal and abnormal meiotic chromo­somes and its relation to the volume of chromosomes. Cytologia, 6: 270-28(). 1935b. do. II. The direction of coiling of chromonema within the first meiotic· chromosomes of the PMC. Jour. Fac. Sci. Hokkaido Imp. Univ., Ser. V., 3: 233-250. 1937a. do. III. The mode of chromatid disjunction at the first meiotic meta­phase of the PMC. Cytologia, 8: 142-177. 1937b. do. IV. Further studies on the direction of coiling of the chromonema within the first meiotic chromosomes. Ibid., 8, 178-194. 1938a. do. VI. On the. nucleolus-chromosome relationship. Ibid., 9: 55-77. 1938b. do. XI. A simple new method for the demonstration of spiral structure

_. I

L'

~48 T. SOEDA

in chromosomes.. Ibid. 9: 243-248. 1941. do. XV. Contribution to t~e present status of knowledge on the mechanism of chromonema coiling. Ibid., 11: 407-428.

-- and T. SUTO, 1935. Contribution to the idiogram stud1 in phanerogamous plants I. . Jour. Fac. Sci. Hokkaido Imp. Univ. Ser. V., 5: 33-75:

NEBEL, B.' R., 1932 Chromosome structure in Tradescantide II. The direction of coiling of the chromonema in Tradescantia reflexa Raf., T. virgi'lllia1l4 L., Zebrina Pend'Ula,Schni~1. and.Rhoeo discolor H~nce. Zeitschr. Zellfor. u. mikr. Anat., 16: 285-304.

OKUNO, S., 1937. Karyological studies on some species of Lobelia. CytologUi, Fujii JubL, Vol.: 897-902.

RESENDE, F., 1937. Uber die Ubiquitiit der SAT-Chromosomen bei den Bliitenpflanzen. Planta, ,.26: 757-807.

SATO, D., 1936a. Chromosome studies in Scilla, II. ,Analysis of karyotypes of Scilla permixta and allied species with special reference to the dislocation of the chromo­somes. Bot. Mag. (Tokyo), 50: 447-456. 1936b, Chromospme studies in Scilla, III. SAT-chromollomes and the karyotypes in AloWiae with special reference to the SAT-chromo!lOme. Cytologia, FujiiJubi., Vol.: 80-'-95. '

SAX, K., 1930. Chromosome structure and the ·mechanism of crossing over. Jour. Arnold Arb., 11: 193-220. 1935. Chromosome structure in the meiotic chromosomes' of Rhoeo discolor Hance. Jour. Arnold Arb., 16: 216-222.

and L. M. HUMPHREY, 1934. Structure of meiotic chromosomes in microsporo­gen~is of Tradescantia·. Bot. Gaz., 96: 353-361.

SOEDA, T. 1942: On the chromos<hnes of Diphylleia Grayi Fr. Schm. Jap. Jour. Genet. 18: 41-48. •

TAYLOR, W. Ro, :t9ih: Chromosome studies on Gasteria III. durinll mikrosporogenesis and the postnieiotic mitosis. 367-387.

Chromosome structure Amer. Jour. Bot., 18.:

TOYOHUKU, T. (the present writer) 1939. The direction of coiling of Jthe chromonema i~ Tradescantia' (in 'Jap!)'nese) .. Jap. Jour. Genet., 15: 310-312.

,

• I

, ,

,.

, I I.

, .